TL;DR Summary

Guppies and Mollies

Guppies and Mollies can live together- under certain conditions. If you are a first-time fishkeeper who is looking for the easiest solution possible- then you won’t like this pair.

Here’s why:

  • 20-gallon tank minimum. Guppies and mollies are both active fish, so they need plenty of swimming space. A good rule of thumb is to have at least 10 gallons of water per 6 inches of fish.
  • Aggression is possible. Male guppies can be aggressive towards each other, so it’s important to keep a close eye on them and separate them if they start fighting.
  • Be prepared for babies. Guppies and mollies are both prolific breeders, which in fishkeeping words means they breed faster than bunnies. This means you’ll need to make some tough choices on who to keep.

If you are comfortable with a bigger tank, like both fish specifically, and don’t mind the fry (baby fish) management then you’ll enjoy the 2 very much.

What's The Difference Between A Molly And A Guppy?

Guppies VS Mollies

guppy icon


When guppies get stressed, they tend to misbehave and may display aggression. Most of the time, they’ll just become sick and die. 

Guppies are striking beautiful fish who are known for their elaborate tails and vibrant colors.

A water temperature of about 78-82 degrees F (25-28 C) and pH between 7 and 8 is required for guppies.

Guppies are omnivores who’ll be happy to eat commercial fish food, live food, and vegetables.

Prolific breeders who give birth to live fry and are known for rapid breeding.

Molly icon


Mollies are also shoaling fish just like guppies and need a minimum group size of 5 to feel safe.

Molly fish can display aggression and territorial behavior when they are stressed. This is usually directly connected to overcrowding. 

Mollies are also beautiful fish with vivid colors- but they are not as impressive as guppies

The same water temperature is needed for mollies, but a pH between 7.5 to 8.5 is necessary. 

Mollies are also omnivores who’ll be happy to eat commercial fish food, live food, and vegetables.

Same as guppies- You can expect A LOT of fry in no time from these prolific breeders

Can I Keep Mollies And Guppies Together?

You can, but you’ll need to make sure your tank is big enough to accommodate the 2. 

20 Gallon Tank Minimum

You can technically get away with a 20-gallon, but the ideal size would be closer to 50.  Because the two fish spit out babies faster than the speed of light you need to be prepared for it with tank size.

I mean, hey- a larger tank is easier to control because it is less sensitive to water quality dropping. 

But a larger tank does take longer to maintain, and if an “oopsie” happens- it’s a way bigger oopsie.

Plenty Of Hiding Spaces

Both fish are pretty shy in nature and don’t like direct confrontation. If you take that away from them in the form of a bar tank- they will resort to violence. 

To guarantee the longevity and health of the tank you’ll need to provide lots and lots of hiding spaces.

I would go for a planted tank with some of my favorite guppy plants.

Which is better guppy or molly?

Whether guppies or mollies are better is a matter of personal preference. Both fish are popular choices for beginner fish keepers because they are relatively hardy and easy to care for. However, there are some key differences between the two species that may make one a better choice for you than the other.


  • Pros: Guppies are very colorful and come in a wide variety of shapes and sizes. They are also relatively inexpensive and easy to find.
  • Cons: Guppies can be more aggressive towards each other than mollies, especially the males. They are also more susceptible to certain diseases, such as ich.


  • Pros: Mollies are generally more peaceful than guppies and are less susceptible to disease. They are also larger and live longer than guppies.
  • Cons: Mollies are not as colorful as guppies and do not come in as wide a variety of shapes and sizes. They can also be more expensive than guppies.

Which one is better for you?

If you are looking for a colorful and easy-to-care-for fish, then guppies are a good choice. However, if you are looking for a more peaceful and hardy fish, then mollies are a better option.

Ultimately, the best way to decide which fish is right for you is to visit your local fish store and talk to the staff. They can help you to choose the right fish for your tank and budget.

Guppies And Mollies Breeding

I’ve mentioned it earlier and I’ll mention it again- both of these fish are basically water bunnies. A single guppy female can spit about 20-100 fry every 30 days. 

if you have 4 female guppies and 4 female mollies you’re looking at anywhere from 160-800 new fish every 30 days. 

Granted, you’re not going to end up with fish in the hundreds, but even 3-4 fish too many can overcrowd a tank and cause it to spiral out of control. 

Can Mollies and Guppies Crossbreed?

Yes, it is possible to crossbreed guppies and mollies. In fact, it happens quite naturally in the wild, where their habitats overlap. The offspring of a guppy and molly cross are called “gollies” or “muppies.”

If you have male and female guppies and mollies in the same tank, it is likely that they will breed at some point. However, there are a few things to keep in mind:

  • The success rate of guppy-molly hybrids is not as high as the success rate of purebred guppies or mollies.
  • Guppy-molly hybrids can be sterile, meaning that they cannot reproduce.
  • Guppy-molly hybrids can have a variety of different physical characteristics, some of which may be undesirable.


Can a black molly and a guppy have babies?

Yes, and have in the past. But the new breed is usually sterile (can’t reproduce) and might have physical characteristics that are undesirable. 

Why is my Molly chasing my guppy?

Possible reasons why a molly might be chasing a guppy:

  • Establishing dominance. Mollies are social fish and like to establish a pecking order. The dominant molly may be chasing the guppy to assert its dominance.
  • Mating behavior. Male mollies may chase female mollies in order to mate with them. If the guppy is female, the molly may be chasing it because it is mistaking it for a female molly.
  • Stress. Mollies can become stressed due to a variety of factors, such as poor water quality, overcrowding, or lack of hiding places. A stressed molly may act aggressively towards other fish in the tank.

How many guppies should be kept together?

A minimum of 5 guppies should be kept together to allow them to remain happy and thriving. 

Will mollies eat guppy fry?

For sure. Mollies will eat a lot of things, and guppy fry is just one of them. No salt of sauce is needed. 

Guppies and mollies size


  • Males: 1-1.5 inches (2½–3½ cm)
  • Females: 1.5-2.25 inches (4-6 cm)


  • Males: 2-3 inches (5-7.5 cm)
  • Females: 3-4 inches (7.5-10 cm)


Guppies and molleis can make great tankmate, assuming your tank is big enough. 

They are both peaceful fish who trhive in the same waters and rely on the same diet.

The downside to pairing the 2 is possible aggression, most likely due to overcrowding. They also breed like crazy which can be challenging to contorl.

And now- a personal favor: now that you know all that you know, what’s your next step? Do you already have a tank or are planning one?

Let me know in the comments!

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